`C_(4)H_(4)O_(4)` may be (Only structural )
1. Saturated dicarboxylicacid
2. Unsaturated dicarboxylic acid
3. Cyclic diester
4. Saturated di aldehyde

Explanation

To determine which structural isomers are possible for the molecular formula \( C_4H_4O_4 \), we will analyze each option based on the degree of unsaturation (DU) and the structural requirements of each type of compound.

### Step-by-Step Solution:

1. **Calculate the Degree of Unsaturation (DU)**:
The formula for calculating the degree of unsaturation is:
\[
\text{DU} = C + 1 - \frac{H}{2}
...